I think it would be worthwhile to contact the manufacturer of that shower base and ask if they have an accessory for this shower base that would lift it off the floor a few inches to allow for the drain piping if you're installing it on a concrete floor.
I really can't think of any good way to support the curved front on that shower pan, except by perhaps putting the drain piping in now, building a "box" to fit around the shower pan (out of 1X6's, maybe), cutting a 5 1/2 inch wide strip of thin plywood ACROSS it's grain so it bends easily and fitting it in your box so that it conforms to the curvature of the front of the pan and turning the whole business over. You could then pour concrete or plaster of paris into that "box" so that you get a flat solid bottom for your shower that already has the plumbing embedded in it.
If you pursue this idea, I'd check with renovators that install shower stalls in people's basements to see if there are any unforeseen problems pouring a concrete or plaster base with the plumbing already in it.
I think the shower base you bought was intended to be installed over a wood floor where a hole could simply be drilled in the floor to provide for the drain piping. I say that because the curved front on this shower pan seems to be particularily difficult to properly support from below.
